AttachedPropertiesContainerLoadEmergencyZeroLogicalProperty field

Attached property for a nullable Boolean for passing on the logical state of the checker assigned to the control (is used, for example, for dependent colouring (false=red, true=green) of a superordinate border in a ControlTemplate): After various failed attempts, the following procedure has proven to be the only viable solution has crystallised: a control superordinate to the ControlTemplate or DataTemplate is assigned the AttachedProperty "LastNotNullLogical": <Expander Name="Exp" Template="{StaticResource ExpanderStyleHeaderCentered}" ... attached:AttachedPropertiesContainer.LastNotNullLogical="{Binding LastNotNullLogical, diag:PresentationTraceSources.TraceLevel=High}" > The AttachedProperty "LastNotNullLogical" is directly linked to "LastNotNullLogical" from is bound to the DataContext, in this case "LogicalNodeViewModel". In the subordinate ControlTemplate, here <ControlTemplate TargetType="ToggleButton"> in LogicalTaskTreeControlStaticResourceDictionary.xaml, DataTriggers are passed to the higher-level Control with Path bound to the AttachedProperty "LastNotNullLogical": <DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Expander}}, Path=(attached:AttachedPropertiesContainer.LastNotNullLogical)}" Value="True"> <Setter Property = "Border.BorderBrush" TargetName="ToggleButtonBorder" Value="{StaticResource ItemBorderBrushGreen}" /> </DataTrigger> <DataTrigger Binding = "{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Expander}}, Path=(attached:AttachedPropertiesContainer.LastNotNullLogical)}" Value="False"> <Setter Property = "Border.BorderBrush" TargetName = "ToggleButtonBorder" Value = "{StaticResource ItemBorderBrushRed}" /> </ DataTrigger> Important note: other solution approaches failed at the latest when the tree orientation was switched.

public static readonly DependencyProperty LastNotNullLogicalProperty

Public Shared ReadOnly LastNotNullLogicalProperty As DependencyProperty

public:
static initonly DependencyProperty^ LastNotNullLogicalProperty

static val LastNotNullLogicalProperty: DependencyProperty